Improved metabolism and body composition beyond normal levels following gastric bypass surgery: a longitudinal study

Abstract

Background: The cardiometabolic risk profile improves following bariatric surgery. However, the degree of improvement in relation to weight-stable control subjects is unknown.

Objectives: To study the differences in cardiometabolic risk profile between formerly obese patients following Roux-en-Y gastric bypass (RYGB) surgery and control subjects.

Methods: Subjects undergoing RYGB and reaching a BMI <30 kg m^-2 2 years postsurgery were matched with control subjects regarding age, sex and BMI. The following examinations were performed: insulin sensitivity measured by hyperinsulinaemic-euglycaemic clamp, insulin clearance, homeostatic model assessment of insulin resistance (HOMA-IR), lipid profile, inflammatory marker levels, dual-energy X-ray absorptiometry and subcutaneous adipose tissue cellularity (fat cell size and number).

Results: Sixty-nine subjects undergoing RYGB were matched to a control subject. Insulin sensitivity measured by hyperinsulinaemic-euglycaemic clamp, blood pressure, inflammatory status and glucose, triglyceride and HDL cholesterol levels were comparable to values of control subjects. However, HOMA-IR (1.0 ± 0.5 vs. 1.3 ± 0.7, P = 0.005), insulin clearance (0.38 ± 0.08 vs. 0.34 ± 0.08 μL m^-2 min^-1 , P < 0.0001) and circulating levels of insulin (31 ± 15 vs. 37 ± 17 pmol L^-1 , P = 0.008), total cholesterol (4.1 ± 0.7 vs. 4.8 ± 0.9 mmol L^-1 , P < 0.0001) and LDL cholesterol (2.1 ± 0.6 vs. 2.9 ± 0.8 mmol L^-1 , P < 0.0001) were improved beyond the levels in matched control subjects. Furthermore, formerly obese subjects had higher lean and lower fat mass as well as a more benign type of adipose cellularity (hyperplasia with many small fat cells) compared to control subjects.

Conclusions: Subjects who underwent RYGB and reached a postobese state demonstrated a beneficial body composition, slightly increased insulin sensitivity as indirectly measured by HOMA-IR and higher insulin clearance, lower atherogenic lipid/lipoprotein levels and benign adipocyte morphology compared with control subjects who had never been obese. In line with previous results, our findings may in part explain why RYGB confers long-term protection against metabolic complications.

Keywords: adipose tissue; body composition; cardiovascular disease risk factors; insulin resistance; obesity; weight loss.